1. Field of the Invention
The present invention relates to a serum/clot separation surface determination apparatus for automatically determining a position of the separation surface (serum-side or clot-side separation surface) of a blood sample that is contained in a test tube and separated into a serum and clot up and down by a silicon-separating medium.
2. Description of the Related Art
In order to accurately separate blood into a serum and a clot using a centrifuge or the like, a separating medium such as a silicon-separating medium is put into a test tube. Using such a test tube including a separating medium, a blood sample containing a serum and a clot that are separated up and down by a silicon separating medium is obtained in the test tube after centrifugal separation.
When the blood sample so obtained undergoes the following processing, it is required that a separation surface of the blood sample, especially a position of the serum-side separation surface be accurately determined. Conventionally, the determination has been performed chiefly by a visual check and using an optical sensor.
In the visual check, it takes time to confirm the position of a separating medium and the separation surface is likely to be determined inaccurately; therefore, there were many cases where an operator could not correctly know an amount of serum included in a test tube. There was a problem that the post-processing was very complicated and a lot of time and trouble was required. On the other hand, the optical sensor complicates the structure of the apparatus since a light-shield means needs to be provided to prevent extraneous light from entering.
An object of the present invention is to provide a serum/clot separation surface determination apparatus having the following advantages.
(a) The serum-side or clot-side separation surface can be determined speedily and accurately and the post-processing can be very simplified.
(b) The apparatus is simple in structure and easy to manufacture.
In order to attain the above object, the serum/clot separation surface determination apparatus according to the present invention has the following characteristic structures. The other characteristic structures will be clarified in the Detailed Description of the Invention.
A serum/clot separation surface determination apparatus according to an aspect of the present invention comprises a test tube containing a blood sample which is separated into a serum and a clot by a silicon separating medium, a test tube holder which holds the test tube, a detection coil fitted on an outer surface of the test tube held by the test tube holder, a measurement signal supply unit which supplies a measurement signal having a given frequency to the detection coil, position control means which variably controls a relative position between the detection coil and the test tube in a longitudinal direction of the test tube by moving at least one of the detection coil and the test tube, signal level detection means which detects a level of the measurement signal that varies with the relative position controlled by the position means, and determination means which determines a position of a sample separation surface obtained by the silicon separating medium, based on the level of the measurement signal detected by the signal level detection means.
The above serum/clot separation surface determination apparatus has the following advantages. The relative permeability of the silicon-separating medium that separates the blood sample into the serum and clot clearly differs from that of the serum or clot. As the drive control unit varies a relative position between the detection coil and test tube, the level of a measurement signal having a given frequency supplied to the detection coil suddenly changes in a position of the silicon separating medium. The signal level detection means automatically detects a point at which the level of the measurement signal increases or decreases suddenly. It is thus possible to accurately determine a position of the sample separation surface.
Consequently, a position of the separation surface between the serum and clot can be determined speedily and accurately, and the subsequent process can be very simplified.
Since the detection coil is used as a sensor, a light-shield means for preventing extraneous light from entering as noise components need not be provided, as compared with an apparatus using an optical sensor or the like. Therefore, the apparatus of the present invention is simple in structure and easy to manufacture.